Adaptive response of equine intestinal Na+/glucose co-transporter (SGLT1) to an increase in dietary soluble carbohydrate.

The study investigates how the digestive system of horses, specifically the small intestine, adapts to an increase in soluble carbohydrate from the diet. The findings reveal that the expression of the Na(+)/glucose co-transporter, SGLT1, linked to glucose absorption, increases significantly in response to a diet high in hydrolyzable carbohydrates.

Introduction to the Study

• The research focuses on the effect of dietary soluble carbohydrate (referred to as hydrolyzable carbohydrate, or hCHO) on horses. This focus is driven by the understanding that consumption of hCHO (which comes from grain) may be a risk factor for equine colic, a common cause of horse mortality.
• The study observes whether horses have the capacity to digest high amounts of hCHO, whether they can sufficiently absorb monosaccharides (the simplest form of carbohydrate), and if they can adapt to a high-carbohydrate diet.

Methodology

• The study assesses changes in the brush-border membrane carbohydrate digestive enzymes and glucose absorptive capacity of the horse’s small intestine. These elements are examined because they play a role in how the horse’s body processes the hCHO.
• To measure these changes, the study uses various forms of analysis, including Western blotting, immunohistorychemistry, Northern blotting, QPCR, and Na(+)-dependent D-glucose transport.
• The horses are grouped into two categories: those maintained on an hCHO-enriched diet and those on pasture forage.
• The diets were designed to gradually switch horses from low hCHO (<1.0 g/kg bwt/day) to high hCHO (6.0 g/kg bwt/day) over two months, and the study recorded the expression levels of SGLT1 in the duodenal and ileal biopsies of these horses.

Findings

• The results showed that horses on the hCHO-enriched diet demonstrated 2-fold higher glucose transport rates, SGLT1 protein, and mRNA expression in the jejunum and 3 to 5-fold higher in the ileum.
• Over time, as horses switched from low to high hCHO diets, the expression of SGLT1 increased 2-fold in the duodenum and 3.3-fold in ileum. In other words, the ability to absorb glucose improved substantially with increased carbohydrate consumption.
• The increase in SGLT1 expression indicates that horses have the ability to adapt to a diet high in carbohydrates by improving their glucose absorption capacity.

Implications

• The findings have important implications for dietary management of horses. Understanding how horses’ digestive systems adapt to high carbohydrate diets offers possibilities for more efficient and safer dietary planning to minimize the risk of colic.